Relative reporting ratio (RRR) is the ratio of how many adverse drug reactions (ADRs) under exposure were actually observed over the number of expected events under the assumption that ADR and drug exposure were independent.
RRR is estimated as:
with p (drug i) denoting the probability of a target exposure being reported, p (ADR j) the probability of the target event being reported and P(drug i, ADR j) the joint probability of a report on the target event under exposure to the target drug.
A RRR value of 1 indicates the normal background noise, e.g., associations by chance. An increase of RRR indicates an overproportional association between the drug and the adverse event. RRR values much lower than 1 indicate a negative association, e.g., the usage of the drug protects the patient from the adverse event.
